It may or may not throw a code. I'm not sure about your '93, but on my '94, it's located on the left side of the upper manifold, kind of underneath the big coolant hose. There are lots of engine diagrams on this site that will help you locate yours. Basically, it measures the amount of vacuum in your system at any given time while the engine is running and regulates the amount of fuel that is traveling to the injectors. If you have a bad FPR, you will be delivering too much (and therefore wasting) or too little gas to the injectors.
If you have a fuel pressure gauge, it's really easy to test. Fuel pressure should be between 30 and 45 psi with the engine running. You also have to do different tests to see how the pressure reacts to vacuum/no vacuum, let it sit for a bit and see how the pressure holds, etc.
It's VERY important to your MPGs that this is functioning properly.